PSAudios 5.1. Invaders From Oxford

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Invaders is based on a script Brendan wrote when he was 18, based around an idea suggested by his brother- "What could the Master do that was so bad, the Doctor could never forgive him?" Brendan's answer won't be revealed as it was not used here, but oddly sort of turned up in the new series at one point, so really he should sue for royalties.

Invaders from Oxford was originally called the The Alternate Faux- a title dropped as the 'Alternate' bit was rendered meaningless and a clever title does not a fun story make (cough Let's Kill Hitler splutter)

In the climax of the story, the Doctor was originally to have plucked out Tom's flat using a tractor beam and brought it aboard the TARDIS, thus giving him access to a historical library. This was dropped because, as we see in The Nelson Identity, it's far more fun just having him mess things up on his own.